The best place for you to wait your guests coming from the international hall. It is possible to pay with your Sodexo card, prices are more expensive than a normal Starbucks.
Good quality coffee and enough space to sit. WiFi wasn’t working when we were there and you have to search for power plugs (tables next to the wall are the trick)!
It is good to have an option that's standardized in historical part of Istanbul. However the stuff can be too invasive sometimes while they are trying to be friendly.
It's already more expensive than usual prices and the staff is the rudest ones I've ever seen at a Starbucks (one of them named Duygu). A total disappointment.